How DPP-4 complicates measuring GLP-1 accurately

How DPP-4 Complicates Measuring GLP-1 Accurately

We know that the proper collection and handling of samples is vital for eliminating analytical variability and improving accuracy when measuring active GLP-1 (7-36) amide.

ALPCO is here to help your lab reduce technical errors and improve assay results when running the STELLUX® Chemi Active GLP-1 (7-36) amide ELISA.

Watch our video series to learn how DPP-4 complicates measuring GLP-1 accurately and how to properly handle GLP-1 samples for more accurate results.

Video Transcript

Hello and thank you for joining us! Have you ever wondered why measuring GLP-1 is so difficult? If so, then this video is for you. Watch our video to learn how DPP-4 complicates measuring GLP-1 accurately. Let’s get started.

Glucagon-like Peptide-1 (GLP-1)

Glucagon-like peptide-1, also known as GLP-1, is a 30-amino acid incretin hormone.

A 3D model of the GLP-1 structure
3D model of Glucagon-like peptide-1 (GLP-1) structure

Function of GLP-1

Over the years GLP-1 has become very important to diabetes and obesity research because it promotes the synthesis and release of insulin which is referred to as the Incretin Effect1. The Incretin Effect helps maintain energy homeostasis1. However, GLP-1 is a very labile molecule which can lead to pre-analytical variability when researchers are trying to measure it in the lab2.

This chart depicts how the incretin effect helps maintain energy homeostasis.
The Incretin Effect helps maintain energy homeostasis

Dipeptidyl Peptidase-4 (DPP-4)

Why is GLP-1 so labile? Well, GLP-1 is actually a substrate for the highly conserved proteolytic enzyme, dipeptidyl peptidase-4, known as DPP-42,3,4. This enzyme is expressed throughout the body in both a membrane bound and soluble form5. Research has demonstrated that DPP-4 cleaves dozens of peptides circulating through the gut, liver, lungs and kidneys, including GLP-15.

A 3D model of the DPP-4 structure
3D model of Dipeptidyl Peptidase-4 (DPP-4) structure8

How DPP-4 Complicates Measuring GLP-1 Accurately

So, when the biologically active form of GLP-1 called active GLP-1 (7-36) amide is secreted from intestinal L-cells in response to nutrient intake, DPP-4 is there ready to cleave the hormone between the second and third N-terminal amino acid residues5. Due to this cleavage by DPP-4, GLP-1 (7-36) amide has a very short half-life in vivo between 1½ – 2 minutes6,7, which reduces the biological effects of active GLP-1 (7-36) amide5.

This image illustrates the formation and degradation of active GLP-1 (7-36) amide.
Formation and degradation of active GLP-1 (7-36) amide

Active GLP-1 (7-36) amide Levels

This means that GLP-1 (7-36) amide is present at low physiological concentrations, making accurate measurements extremely difficult, particularly in fasted subjects who already have low levels of active GLP-12.

This chart demonstrates Active GLP-1 (7-36) amide fasted vs. fed levels following oral glucose challenge tolerance test (OGTT).
Active GLP-1 (7-36) amide fasted vs. fed levels following oral glucose challenge tolerance test (OGTT).
This chart illustrates Active GLP-1 (7-36) amide fasted vs. fed levels following the mixed meal tolerance test (MMTT).
Active GLP-1 (7-36) amide fasted vs. fed levels following the mixed meal tolerance test (MMTT).

Proper Sample Collection and Handling

However, research has demonstrated that the can preserve active GLP-1, aid in the elimination of pre-analytical variability, and improve accuracy when measuring active GLP-1 (7-36) amide levels2,3,4.

Are you experiencing issues measuring GLP-1 in your lab? Be sure to check out our next video for a complete guide to support your sample collection and handling processes when running our STELLUX® Chemi Active GLP-1 (7-36) amide ELISA.

References

  1. Sandoval and D’Alessio (2015). Physiology of proglucagon peptides: role of glucagon and GLP-1 in health and disease. Physiol Rev. 2015 Apr;95(2):513-48. doi: 10.1152/physrev.00013.2014. PMID: 25834231.
  2. Yi, et al (2015). Degradation and stabilization of Peptide hormones in Human Blood Specimens. PLoS One. 2015 Jul 29;10(7):e0134427. PMID: 26222180.
  3. Bielohuby, et al (2012). A guide for measurement of circulating metabolic hormones in rodents: Pitfalls during the pre-analytical phase. Mol Metab. 2012 Aug 9;1(1-2):47-60. PMID: 24024118.
  4. Wewer Albrechtsen, et al (2015). Stability of glucagon-like peptide 1 and glucagon in human plasma. Endocrine Connections, 4:50-57. PMID: 25596009.
  5. Mulvihill and Drucker (2014). Pharmacology, Physiology, and Mechanisms of Action of Dipeptidyl Peptidase-4 Inhibitors. Endocr Rev. 2014 Dec;35(6):992-1019. PMID: 25216328.
  6. Holst (2007). The Physiology of Glucagon-like Peptide 1; Physiol Rev. 2007 Oct;87(4):1409-39. PMID: 17928588.
  7. Deacon, et al (1995). Degradation of glucagon-like peptide-1 by human plasma in vitro yields an N-terminally truncated peptide that is a major endogenous metabolite in vivo; J Clin Endocrinol Metab. 1995 Mar; 80(3):952-7. PMID: 7883856.
  8. Rose et al. (2018) NGL viewer: web-based molecular graphics for large complexes. Bioinformatics doi:10.1093/bioinformatics/bty419), and RCSB PDB.